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  • Author Author: aemarconnet
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Review of Agilent U1620A 200MHz Handheld Oscilloscope

aemarconnet

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RoadTest: Agilent U1620A 200MHz Handheld Oscilloscope

Author: aemarconnet

Creation date:

Evaluation Type: Independent Products

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?:

What were the biggest problems encountered?: Energy would couple across input channels, making both channels "noisy". Please see detailed review section: "NOISE ON INPUT CHANNELS".

Detailed Review:

First and foremost this is an amazing device at a great sales price considering how feature-packed it is. It has been a lot of fun, convenient, and very exciting to work with. It performs well across the board and is loaded with useful features. During my road test of this device it has been an invaluable asset easily worth the ~$3000 commercial cost. It has aided in dignostic and support work in the RF industry and performed well.

 

 

I hesitate to use such a subjective measurement as the "5 star review scale", but it seems to have become ubiquitous of the online market place. I would gladly award this device a 5 star review save for 1 problem that i experienced with RF coupling across channels (see the section on “Noise in output channels”). Taking that into consideration i believe that it still would deserve a 4 to 4.5 stars, and would re-award 5 stars if a work-around like the one I created was commercially available.


 

The U1620A is rugged, useful, powerful, feature packed, extreemely accurate and quite reliable.

With the above underlined statement, i would like to go into some of the problems, concerns, and limitations of the device.

 

 

INITIAL THOUGHTS

When I received the unit in the mail I felt like I hit the jackpot and rushed to open it, sadly, it needed to be fully charged prior to use, however I can say that my initial reaction was the following:

I was very impressed with the rugged exterior, the silicon buttons provided a good tactile response and the unit was surprisingly small and light considering how much technology must be crammed inside. The handle (fabric and Velcro) took a bit of getting used to.

It seems that the device is intended to be held with the right hand in the strap, supported by the left forearm. I would have liked to have seen mounting brackets for a right handed individual (so that the right hand is free to use probes and operate the unit). Regardless, after a few hours one becomes accustomed to holding it, and often I have the unit sitting on a ledge or table near my device under test.

 

 

DISPLAY

On the first day operating the product, I had a blast; I took it to every electrical source I could find in my facility. The display was very bright and clear, and the user interface was quite intuitive. I even took the opportunity to get it outside to see how the monitor looked in the sunlight. I was quite impressed by how readable the display was in the “outdoor” mode. Even on a bright sunny day text and scope measurements were quite clear.

 

 

NECK AND SHOULDER STRAPS

While examining the noise in the electrical system of my 2007 Toyota Highlander (with and without filtering capacitor) The Supplied neck-strap broke and the device fell 3 feet...there is some minor scuffing, however the rubberized case absorbed the impact well. I was rather dissatisfied that a $3000 piece of equipment was shipped with such a cheap strap; in addition to being physically weak (poorly designed seam between strips of fabric) it feels cheap compared to the actual handheld unit. On another note: I would have loved to see neoprene used to make the strap more comfortable, in an un-collared shirt it can chafe a good bit around the neck…while on the subject of straps the hand strap, when adjusted to accept a larger hand, does not have sufficient strength. On multiple occasions the velcro has released and thus i nearly drop the device.

 

 

PRECISION CONTROL - Lacking

From the very beginning, when taking measurements I longed for some form of precise input. The range, position, and time controls are all operated with up/Down +/- type controls. This method of controlling the input seemed too clunky and did not give me the control that I desired. I greatly missed having a knob-style input that is standard with desktop scopes. I understand that such a knob would compromise the ruggedness of the device, however a low profile solution could be found similar to the knobs seen in DJ Audio Equipment. Via software a single “universal” knob could easily be designated to control whichever button had been last used (eg if one were to tap the “time scale” to a longer span, then turning said dial would allow fine-tuning of that input)….along the same lines I would also like to see the addition of a num pad or mini-keyboard, it seems that the device has limited “USB On-The-Go” support, I would like to see USB support for a keyboard.

 

 

MEMORY SLOT NAMES

I work in a manufacturing facility and I manage multiple products. When I started saving data to the internal memory I was disappointed to find that these files were names solely based on the memory “Slots” and timestamps. Even saving to an external flash drive one is limited to the timestamp. This does not allow me to keep track my data, I have to keep a notebook to log when I was measuring what device.

 

 

SOFTWARE INSTABILITY (FIRMWARE UPDATE CORRECTED?)

During my first few days using the device I experienced multiple instances of a very similar software crash. This particular crash appeared as though the display froze and during a refresh cycle the majority of the screen was wiped to black. Leaving only small fragments of the Background grid still illuminated on the display…There was no real pattern behind this crash…I would simply be navigating the menu and suddenly it would occur…Later, I updated to the latest firmware, and since then have not experience this error.

 

 

!!!!!!!NOISE ON INPUT CHANNELS!!!!!!!!!

This following error is perhaps the most frustrating for me. Working with the high frequencies, high voltages, high noise (electromagnetic), and high powers associated with the RF industry I immediately took note of the poor isolation/shielding between channels.

To state it as simply as I can: when only one line of the scope was in use I saw amazingly clear plots of the waveform. However when the second channel was activated I began to see a great deal of noise, to the point where the waveform looked nothing like it should. In some instances I even noticed that the shielding channel 2 with my finger would wildly manipulate channel 1. Unfortunately I cannot provide images as the content is proprietary. However, I realized that by making the unit portable we sacrifice a proper ground, and to make it compact we sacrifice shielding: as such, both channels psudo-float at a potential and energy is able to somehow couple between channels. Especially when both inputs have a high frequency/power input, we see inductive(?) coupling of this energy to the other channel of the scope. In my experimentation I found that the trick to reducing noise is to provide a common ground. My initial testing was simply done with a paperclip: bent to contact the outer conductor  of each channel (CH1, CH2, Trig). This was very successful, but it was difficult to maintain a good connection with the paper clip, I plan to produce a better common ground using 3 coax elbows linked with wire. If hardware modifications are not made to the devices next generation to combat this problem, I would recommend that such a “grounding Compensator” be made commercially available.

 

 

BATTERY DISPLAY

Since upgrading to the latest firmware I have noticed that the battery life is not accurately displayed on the device. It will show the red low-power icon even when the display on the battery shows a full charge. I believe that the icon simply gets “stuck” as it no longer shows the “charging” icon either. This can be re-set by pulling the battery, simply power-cycling the unit does not always fix the icon.

 

 

LOGGER REFRESH RATE

During my experience with the device I found that that the fixed refresh rate of apprx 1 sample per second was insufficient. When working with some equipment it is important to be able to react quickly. To be able to see a trend and prevent a fatal malfunction that second can make a world of difference. I think that it would be nice if the user were able to change a setting to sacrifice some of the accuracy (decimal points) and increase the refresh rate to at least 2 Hz if not more. I am unsure if this could be done within the software/firmware, or if it would require a hardware change, but I believe that it is a feature that is well worth looking into.

 

 

LOGGER DISPLAY

When in the Data Logger mode this unit shows a plot of the measurement against time. As time progresses the unit automatically scales the division of time such that all time is displayed. This can make it hard to visually examine the rate of change. I believe fixed width (Rolling option) would be a worthy addition (eg trim to only show the last 30 seconds of data).

 

 

USB DAQ INTERFACE

I have done some experimentation, however I have been unable to configure the device for use as a Data Acquisition module via USB. I think that integration with labview or even excel could increase the utility of this hardware.

Anonymous
  • in reply to aemarconnet

    Isolated channels and noise problem

    The feature "isolated channels" is designed for industrial applications where the power line voltage signals, say 480VAC, are well protected and isolated from other channels.  (The U1620A is rated for Cat III 600V applications)  This feature turns out to be a problem in your high frequency AC applications, as you well noted.  The small stray AC coupling between channels becomes significant as the frequency increases.

     

    From the scope manufacturer's point of view, the isolation feature is expensive to implement.  Ironically, this expensive feature actually has to be defeated for the scope to work in your application.  Cheers for paper clips.  We could either have a "grounding compensator" or elimination of the isolated channel feature. 

     

    P.S. Would shorting the grounding clips together work?

  • in reply to DAB

    Collapsing Time

    I am not quite sure what you mean by "collapsing" time. If you are referring to the Data logger, then yes, you can save these data to a flash drive an review it with a software like MS Excel, or any program capable of opening a *.CSV file.

     

    In college i was taught quite a few software codes, but as a real engineer, i find that most any useful data analysis can be done with just Excel and some macros/VBA code. I suspect that a good chunk of the customer base for this product feels the same way, so i would hope that they would develop a better platform for "slaving" the U1620A directly to the computer.

     

    Once again, You can export as a *.CSV file (comma separated values) directly to a flash drive, and this feature works very well. But you cannot give the files "useful names" (ie type in a name), the names are generated from a time-stamp. The same concept goes for the input, i wish i were able to label the inputs with names like "RF in" and "Current Pulse" rather than "Channel 1" and "Channel 2".

     

    The unit can save data directly to USB disks, i have only saved to flash drives (16gb sandisk ultra FAT32 & 64GB patriot Rage EXTFAT), but i believe that the NTFS file system is also supported, so a USB hard drive should work as well. The Scope can export images as Bitmap or Jpeg, and data as a CSV file. The data logger can also do the same. The device settings can be saved with or without a trace to the internal memory, but i am unable to retrieve the "trace" (Image of a pulse) from the device when saved in a "memory slots".

     

    Let me give you some background of my work and typical setup so that i can explain the noise issue better.

    I have operated the device with a variety of RF generating devices and i have witnessed this issue on all. A pulsed magnetron is driven by a Pulse-Forming-Network that provides a high voltage pulse between the cathode and anode. This pulse causes electrons to be emitted from the cathode into the interaction space. Through a great deal of particle physics and electromagnetics: RF energy is created and coupled out of the device. This RF energy travels through waveguide to a load. Using a directional coupler, we are able to extract a portion of that RF energy and attenuate it to a level that a crystal detector is able to handle. The output of the crystal detector is a standard Co-Ax terminal which can be connected to the scope.

     

    When observing a magnetrons operation engineers typically look at the Current pulse, and the RF. To look at the current pulse a torroid (also called a current transformer) is used. I can't give you specifics of any of my devices, but after the current transformer the scope will see about 1-3Volts on channel 1. The RF, after attenuation is typically a matter of 500-5000 milliVolts on channel 2. In a typical weather radar the pulses are only a few microseconds long.

     

    With the unit un-grounded: If i were dealing with a 1V, Near-Square, current pulse, i would actually see not only rounded corners, but lengthy leading and trailing edges. In a 5 Microsecond pulse there can be 1 Microsecond leading edge and a 3 microsecond trailing edge. The noise itself is worst at the beginning of the pulse where it can Spike and Valley such that at one moment it may be 0V and a fraction of a microsecond later it is measuring nearly 2V (from a 1V signal)...it's almost comical, but it often reminds me of the profile of a porcupine.

    With my auxiliary grounding in place, i see the curve that i would expect to see on any of my "desktop" units: A Square wave with some slight rounding of the corners.

     

    I'll see about taking better measurements of this, and try to force it it to couple energy at home so that i can show you a non-proprietary example.

     

    Battery

    Lately i have been using the unit without the batter cover in place. The On-Screen battery display lies to me, so i look directly at the display built into the battery. I'm not one to use the unit till it just shuts down, but i would say that i get between 4-6 hours of use out of each charge. It varies depending on what work i'm doing, and how bright i have the display set.

     

    This battery life has not really changed over since i have had the unit. It has stayed at about 5 hours per charge.

     

    Movie Recording?

    I think that it would be neat if the unit were capable of recording a "Movie" of the scope display. When dealing with a faulty Magnetron (microwave power source) often we will see the RF pulse collapse intermittently, it is very difficult to save/capture these instances with the software. In my industry the percentage of missed pulses / malformed pulses is a measure of the quality of the device, taking only one snapshot of the operation is not sufficient to show how well the device is operating. So this feature would be very useful.

  • Good review.

     

    I like how you addressed each issue with a good honest assessment.  Some of us rely on these types of information when we are considering a purchase for a new device.  We need to know as much about its working life as possible.

     

    The collapsing time issue is one that is common for the switch from Analog to Digital scopes.  The ability to collect the data is essential for full analysis.  Does the scope give you the ability to drill down in the time line to see specific signal captures?

     

    I like your idea about exporting the data to excel, I had the same thought when I applied for the road test.  Most of my work involves short lived EM events which require a lot of post capture data analysis.

     

    Can the unit store data directly to a USB stick?

     

    Do you have any measurements on the input noise issue?  Are we talking 20db or 3 db, see if you can get us some measurements over the frequency spectrum.

     

    Do you have any numbers on the hours per use per charge?

    Have you tried using the device on all day to see if it degrades over time?

     

    Just a thought,

    DAB